Work Vehicle Having Hydraulic Apparatus

ABSTRACT

Disclosed is a work vehicle having a hydraulic apparatus which can reliably prevent erroneous operation of the valve of the hydraulic apparatus even when the operating lever is moved inadvertently. With this hydraulic apparatus, with operations of a single operating lever in two directions, two valves are operated respectively. Two valve operating links for operating the two valves respectively are pivotally supported to a support shaft provided to a pair of frame plates and a lock pin is provided to the frame plates. The two valve operating links form pin holes. When the two valves are at the neutral positions, the lock pin is inserted into the pin holes with a locking operation of a lock operating tool, thus fixing the valve operating links and locking the valves.

CROSS REFERENCE RELATED TO APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 12/725,049 entitled “Work Vehicle Having Hydraulic Apparatus”filed on Mar. 16, 2010 which claims priority to Japanese PatentApplication Nos. 2009-231791 and 2009-231838, both filed on Oct. 5,2009, the entire disclosures of which are herein incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a work vehicle having a hydraulicapparatus. More particularly, the invention relates to a hydraulicapparatus wherein two valves for two hydraulic units are operablycoupled to a single operating lever, which lever is operable in a firstdirection and a second direction intersecting the first direction, andthe valves are operated individually by operating the operating lever inthe first and second directions, respectively.

2. Description of the Related Art

JP 2008-245609 A discloses a technique according to which a single leveris operated in two directions for individually operating two valves inthe first direction and in the second direction, respectively. Moreparticularly, according to the technique disclosed in this JP2008-245609 A, a coupling mechanism provided between the two valves andthe operating lever incorporates two valve operating links connectedrespectively to the valves. These two valve operating links are mountedto a frame plate having an angular hook-like cross sectional shape, withthe operating links being mounted in opposition to each other along thefront/back direction. The frame plate supports cantilever-wise two bossportions, one boss portion supporting a support shaft oriented along theright/left lateral direction for operating the operating lever in thefront/back direction, the other boss portion slidably receiving thereina lock pin in the right/left lateral direction. In operation, when theoperating lever is located at its neutral position, the lock pin will beoperated to be inserted into the boss portion formed integrally with theoperating lever, thereby locking this operating lever. With this, thetwo valves can be fixed at the neutral positions.

According to the above-described technique disclosed in JP 2008-245609A,with insertion of the single lock pin into the boss portion formedintegrally with the operating lever, the operating lever is lockedrelative to the direction intersecting the lock pin and the insertingdirection to the boss portion. Therefore, if there exist a large gapbetween the boss portion slidably supporting the lock pin and the lockpin and a large gap between the boss portion formed integrally with theoperating lever and the lock pin, if this operating lever is operatedinadvertently under the locked condition of the operating lever, thelocking boss portion tends to slide in the axial direction of the lockpin, whereby the one valve operating link may be operated erroneously tomove the valve.

The object of the present invention is to provide a work vehicle havinga hydraulic apparatus which can reliably prevent such erroneousoperation of the valve of the hydraulic apparatus even when theoperating lever is moved inadvertently.

SUMMARY OF THE INVENTION

The above-noted object is fulfilled according to an aspect of thepresent invention as under:

A work vehicle having a hydraulic apparatus, comprising:

-   -   a single operating lever;    -   a first valve operable by an operation of the operating lever in        a first direction;    -   a second valve operable by an operation of the operating lever        in a second direction intersecting the first direction;    -   a first valve operating link pivotally supported to a support        shaft of the operating lever, the first valve operating link        supplying/draining pressure oil to/from a first hydraulic unit        via the first valve;    -   a second valve operating link pivotally supported to the support        shaft of the operating lever, the second valve operating link        supplying/draining pressure oil to/from a second hydraulic unit        via the second valve;    -   a pair of frame plates disposed in opposition to each other        across the first and second valve operating links therebetween;        and    -   a boss portion supported by the pair of frame plates and        supporting the support shaft of the operating lever;

wherein:

-   -   the pair of frame plates include a lock pin;    -   the first valve operating link defines a first pin hole;    -   the second valve operating link defines a second pin hole; and    -   when the first valve and the second valve are located at neutral        positions thereof, the first and second valve operating links        are fixed to lock the first and second valves by inserting the        lock pin into the respective pin holes.

With this construction, the pair of frame plates disposed in oppositionacross the valve operating links therebetween hold the boss portion forsupporting the support shaft of the operating lever from the opposedsides thereof, so that the frame plates per se are formed sturdy and theboss portion too is firmly supported to the frame plates. Even when theoperating lever is operated in two directions, there occurs no loosenessor displacement of the boss portion, so that its support shaft can besupported in a reliable manner. Hence, there occurs no displacement inthe operations of the operating lever in the first direction and thesecond direction, and the operating lever can be operated lightly andsmoothly.

When the two valves are at the neutral positions, by inserting thesingle lock pin into the plurality of pin holes defined in the two valveoperating links, these two valves are locked at the same time. That is,the two valve operating links are directly locked with insertion of thesingle pin into the holes defined in the two valve operating linksprovided respectively for operating the two valves. Therefore, even ifthere exists some play on the side of the operating lever, the twovalves can be locked at the neutral positions in a reliable manner.

Further, as the valve operating links, the boss portion supporting thesupport shaft of the operating lever, the lock pin, etc. are supportedto the pair of frame plates, these components can be manufactured as oneintegral unit (assembly) and assembled as such to the work vehicle.

Therefore, since both the valve operable by the operation of theoperating lever in the first direction and the further valve operable bythe operation of the operating lever in the second direction can belocked at the respective neutral positions thereof reliably, even if theoperating lever is moved inadvertently, erroneous movements of thevalves can be prevented in a reliable manner.

Since the pair of frameworks (the valve operating links, the bossportion, the lock pin, etc.) can be formed as a single unit (assembly),the productivity can be improved.

In the above-described construction, preferably, the lock pin issupported to one of the pair of frame plates when the locking of thevalves is released; whereas, the lock pin is supported to both of thepair of frame plates when the valve operating links are fixed forlocking the first and second valves. With this construction, a furtheradvantage as follows can be achieved.

Namely, when the valve operating links are fixed for locking the valves,the lock pin is supported from both sides thereof by pair of frameplates. So, the valves can be fixed and maintained in a more reliablemanner than the case of the valves being locked by the lock pin underits one-side supported state, i.e. cantilevered state. As a result, thevalves can be locked at the neutral positions with even greaterreliability.

The present invention provides a further characterizing feature asunder:

A work vehicle having a hydraulic apparatus, comprising:

-   -   a single operating lever;    -   a first valve operable by an operation of the operating lever in        a first direction;    -   a second valve operable by an operation of the operating lever        in a second direction intersecting the first direction;    -   a locking mechanism for locking the operating lever at a neutral        position thereof, the locking mechanism including:        -   a concave member attached to one of a movable support            portion and a base portion of the operating lever, the            concave member defining a concave portion at an end thereof;        -   a clamping member attached to the other of the movable            support portion and the base portion of the operating lever            for clamping the concave member, the clamping member            including a pin engageable with the concave portion;    -   wherein, when the operating lever is at the neutral position,        the operating lever is locked to be immovable in the first or        second direction by moving the support portion to cause the        clamping member to clamp the concave member and also to cause        the pin to engage the concave portion.    -   The above-described construction provides two functions to the        concave member—the concave member per se provides a function as        an engaged member to be clamped by the clamping member and the        concave portion of this concave member provides a function as a        further engaged member to be engaged by the pin included in the        clamping member. Similarly, the clamping member also provides        two functions of clamping the concave member and the engagement        with the concave portion with the pin. Hence, with respective        engagements of these, by the two functions on each side, the        locking of the operating lever in the first direction and the        locking of the operating lever in the second direction are        effected.

That is to say, with the two kinds of engagement, i.e. the clamping ofthe concave member by the clamping member (first engagement) and theengagement between the concave portion of the concave member and the pinof the clamping member (second engagement), the operating lever islocked against its movement in two directions, i.e. the first directionand the second direction individually. With this, the locking operationsof the operating lever both in the first and second directions can beprovided in a reliable manner.

-   -   Since the locking operations of the operating lever in the first        direction and the second direction can be provided in a reliable        manner, the locking mechanism of the operating lever can be used        for an extended period of time.

In the above-described construction, preferably, the support portioncomprises a pivotable and fixable support shaft, and when the operatinglever is located at the neutral position, the operating lever is lockedto be immovable in the first or second direction by pivoting the supportshaft. With this construction, a further advantage as follows can beachieved.

Namely, the locking operation and the lock-releasing operation of theoperating lever can be effected by pivoting the concave member of thelocking mechanism or the support shaft including the clamping member.Hence, the locking and lock-releasing operations of the operating levercan be effected easily and conveniently.

Still preferably, there is provided holding means for holding a lockedcondition provided by the engagement between the concave member and theclamping member and also holding a lock-released condition provided bydetachment between the concave member and the clamping member. Withthis, inadvertent locking or lock-releasing of the operating lever whenthe operating lever is to operated can be prevented in a reliable manner

Further and other characterizing features and advantages resultingtherefrom of the present invention will become apparent upon reading thefollowing detailed description of the preferred embodiments thereof withreference to the accompanying drawings.

In the following, the respective embodiments will be described by takinga tractor as an example of the work vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-9 show a work vehicle (tractor) according to a first embodimentof the present invention; in which,

FIG. 1 is a partial side view of the tractor mounted with a frontloader,

FIG. 2 is a side view of an operating section of a switchover valve,

FIG. 3 is a rear view of the operating section of the switchover valve,

FIG. 4 is a plan view of the operating section of the switchover valve,

FIG. 5 is a plan view in horizontal section of a support portion of anoperating lever,

FIG. 6 is a plan view in partial horizontal section showing an operatingportion of the switchover valve,

FIG. 7 is a side view in partial vertical section of a lockingarrangement of a valve operating link,

FIG. 8 is a perspective view showing an operating portion of theswitchover valve, and

FIG. 9 is an exploded perspective view of the valve operating link,

FIGS. 10-16 show a work vehicle (tractor) according to a secondembodiment of the present invention; in which,

FIG. 10 is a side view of an operating section of a switchover valve,

FIG. 11 is a rear view of the operating section of the switchover valve,

FIG. 12 is a plan view of the operating section of the switchover valve,

FIG. 13 is a plan view in partial horizontal section showing anoperating portion of the switchover valve,

FIG. 14 is a side view in partial vertical section of a lockingarrangement of a valve operating link,

FIG. 15 is a perspective view showing the operating portion of theswitchover valve, and

FIG. 16 is an exploded perspective view of the valve operating link,

FIGS. 17-22 show a work vehicle (tractor) according to a thirdembodiment of the present invention; in which,

FIG. 17 is a side view of the tractor mounted with a front loader,

FIG. 18 is a perspective view showing an operating mechanism of anoperating lever for operating two valves,

FIG. 19 is a rear view showing the operating mechanism of the operatinglever for operating the two valves,

FIG. 20 shows a lever locking mechanism, (a) being a side view showing alock-released condition, (b) being a side view showing a lockedcondition,

FIG. 21 shows the lever locking mechanism, (a) being a side view invertical section showing the lock-released condition, (b) being a sideview in vertical section showing the locked condition, and

FIG. 22 is a plan view showing the lever locking mechanism.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

FIGS. 1-9 show a work vehicle (tractor) according to a first embodiment.In this embodiment, FIG. 1 is a partial side view of a tractor mountedwith a front loader R. This tractor includes a traveling vehicle body 3having front wheels 1 and rear wheels 2, the body 3 mounting a driver'sseat 4, a front-wheel steering wheel 5, a driver's access step 6, etc.

The traveling vehicle body 3 is formed by connecting a vehicle bodyfront section mounting an engine (not shown) and a transmission case 9provided in a vehicle body rear section via an intermediate housing 10having a hollow construction formed of metal plates. The engine iscovered with a hood 11, and to a front frame 12 connected to the engine,there is supported a front axle case 13 mounting/supporting theright/left front wheels 1 to be steerable, with the front axle case 13being capable of a rolling action. And, the rear wheels 2 are supportedto right/left rear portions of the transmission case 9.

The power of the engine is shaft-transmitted to a hydrostatic steplessspeed-changing unit (HST) 14 directly connected to the front end of thetransmission case 9, so that the engine power is speed-changed instepless manner in the forward and reverse directions. This forward orreverse, speed-changed power is further speed-changed by gears in aplurality of speed steps inside the transmission case 9 and front-wheeldriving power taken off from the rear wheel transmission line isshaft-transmitted to the front section of the vehicle body to betransmitted to the front axle case 13.

A part of the engine power inputted to the stepless speed-changing unit14 is transmitted as it is, i.e. without being speed-changed, to a PTOtransmission line provided inside the transmission case 9, so that thispower can be taken off from a rear PTO shaft (not shown) mounted at arear portion of the transmission case 9 and a mid PTO shaft 16 mountedat a lower portion of the transmission case 9, as a “live PTO power”which is rotated at a fixed speed, regardless of the traveling speed.

On the right side of the driver's access step 6, there is provided aspeed-changing pedal 17 urged to return to its neutral position and thispedal 17 is link-coupled to an unillustrated speed-changing operatingshaft of the stepless speed-changing unit 14. Forwardly of the rightside of the driver's access step 6, there are provided a pair ofright/left side brake pedals 18.

To the front portion of the traveling vehicle body 3, the front loader Ris detachably attached. A hydraulic apparatus for driving this frontloader R is constructed as follows.

On the right side of the driver's seat 4, a switchover valve 25 isfixedly mounted, and an operating lever 26 for switching over thisswitchover valve 25 extends first forwardly and then upwardly. As shownin FIGS. 1-4, the switchover valve 25 includes two, three-positionswitchover type, spool valves 23, 24 mounted in juxtaposition in thefront/back direction, to be operably coupled with an operating lever 26as will be described later. With crisscross operations of the operatinglever 26, feeding/draining of pressure oil to/from the two sets ofhydraulic circuits is possible.

On the right side and forwardly of the driver's access step 6, four pipeconnecting members 28 having automatic closing type pipe connectingports 28 a are mounted vertically in series, with each pipe connectingmember 28 and the switchover valve 25 being connected and communicatedto each other via four metal pipes 29.

Referring to the front loader R, to a support frame 31 connected andfixed to front right/left portions of the traveling vehicle body 3, aboom 32 is connected to be vertically pivotable. And, a bucket 33 ispivotally connected to the leading end of the boom 32 to be capable ofpivotal dumping actions. And, a boom cylinder 34 and a bucket cylinder35 which comprise double-action type cylinders are connected andcommunicated to the four pipe connecting members 28 viapressure-resistant hydraulic hoses 36, respectively.

FIGS. 2-9 show an operating construction of the switchover valve 25.Upwardly of a valve body 25 a of the switchover valve 25, a pair ofsupport brackets 40, 41 are mounted erect, as “a pair of frame plates”on the front and rear sides and spaced apart by a predetermined distancetherebetween across valve operating links 38, 39. At the upper end ofone (rear side) support bracket 40, there is formed a bent portion 40 aextending toward the other (front side) support bracket 41. To andbetween an end of this bent portion 40 a and the other support bracket41, there is fixed a right/left oriented boss portion 42, with the bossportion 42 being supported in a longitudinal direction along an axis (x)of a right/left oriented support shaft 30.

A first operating tool 43 having an angular hook-shape cross section ismounted to be pivotable about the lateral axis (x) and to this firstoperating tool 43, a second operating tool 44 is pivotally attached tobe pivotable about a front/back oriented axis (y). And, to the upperface of this second operating tool 44, a base end portion 26 a of theoperating lever 26 is fixed.

The pair of front and rear support brackets 40, 41 respectively defineboss portions 46 for supporting a front/back oriented support shaft 45and this front/back oriented support shaft 45 supports boss portions 38a, 39 a provided at the base ends of the valve operating links 38, 39 tobe vertically pivotable about an axis (a). Respective free ends of thesevalve operating links 38, 39 are connected respectively to the spoolvalves 23, 24 via pins 47.

As shown in FIG. 3, the working points (the positions of the pins 47) onthe side of the spool valves 23, 24, the axis (a) (pivot) of thefront/back oriented support shaft 45 and coupling members 48 b, 49 b(power points) are aligned side by side along a straight line L in therear view, and also, a lock pin 55 is disposed immediately upwardly ofthe axis (a) (pivot) of the front/back oriented support shaft 45.

The valve operating link 38, 39 each includes a boss portion 38 a, 39 afor allowing insertion of the front/back oriented support shaft 45, anarm portion 38 c, 39 c having a U-shape in the plan view defining a slot38 b, 39 b for allowing insertion of a pin 47 for connection of thespool valve 23 at the other end relative to the boss portion 38 a, 39 aas the base end, a two-forked shaped arm portion 38 e, 39 e having abent piece 38 d, 39 d formed on the opposite side away from the armportion 38 c, 39 c relative to the boss portion 38 a, 39 a.

As shown in FIG. 2, FIG. 4 and FIG. 5, from the first operating tool 43,an operating arm 43 a extends rearwards, and from the second operatingtool 44, an operating pin 44 a extends inward in the right/leftdirection. The operating arm 43 a and the bent piece 39 c of the onevalve operating link 39 are operably coupled with each other via a rod48 mounting coupling members 48 a, 48 b with spherical pivots at theopposed ends thereof; and operating pin 44 a and the bent piece 38 d ofthe other valve operating link 38 are operably coupled with each othervia a rod 49 mounting coupling members 49 a, 49 b with spherical pivotsat the opposed ends thereof.

Therefore, when a grip 26 b of the operating lever 26 is located at aneutral position in the front/back and right/left directions, the twospool valves 23, 24 are located at the respective neutral positionsthereof. When the grip 26 b of the operating lever 26 is moved forwardlyor rearwardly from the neutral position, the first operating tool 43 ispivoted about the laterally oriented axis (x), whereby one spool valve24 is slid vertically. When the grip 26 b of the operating lever 26 ismoved to the left or right side from the neutral position, the secondoperating tool 44 is pivoted about the front/back oriented axis (y),whereby the other spool valve 23 is slid vertically.

When the front loader R is mounted, the boom cylinder 34 ispipe-connected to the hydraulic circuit that is switched over by onespool valve 24, whereas the bucket cylinder 35 is pipe-connected to thehydraulic circuit that is switched over by the other spool valve 23. Inthis case, when the grip 26 b of the operating lever 26 is operatedforward from the neutral position, the boom cylinder 34 is contracted tolower the boom 32, whereas, when the grip 26 b of the operating lever 26is operated rearward from the neutral position, the boom cylinder 34 isexpanded to elevate the boom 32. When the grip 26 b of the operatinglever 26 is operated to the right side from the neutral position, thebucket cylinder 35 is expanded to dump the bucket 33 downwards; whereas,when the grip 26 b of the operating lever 26 is operated to the leftside from the neutral position, the bucket cylinder 35 is contracted toelevate the bucket 33 for its scooping-up operation. In this way, thepiping system is configured.

To the boss portion 38 a of the valve operating link 38 and the armportion 39 e of the valve operating link 39, there are mounted erectlocking brackets 51, 52 oriented upwards, respectively. And, at upperportions of the brackets 51, 52, there are defined lock pin hole 51 a,52 a. The front and rear support brackets 40, 41 faun boss portions 53,54, and into the elongate boss portion 54 attached to the supportbracket 41, there is inserted a lock pin 55 for mechanically fixing theoperating lever 26 at its neutral position. At an outer end (front end)of the lock pin 55, there is fixed a downwardly oriented L-shapedholding portion 55 a. To the outer side (front side) of the supportbracket 41, there is attached a horizontal receiving plate 56 definingtwo engaging holes 56 a, 56 b. The lower end of the L-shaped holdingportion 55 a is placed, due to the weight of its own, in slidablecontact with the upper face of the receiving plate 56.

The lock pin 55 is operable by a crank-shaped lock operating tool 57.The lock operating tool 57 includes, at its lower end, an arm 58engageable with the holding portion 55 a of the lock pin 55. The arm 58includes a slot 58 a for engagement with the holding portion 55 a and adownwardly oriented positioning pin 58 b.

The lock operating tool 57 includes, at its upper portion, a downwardlyoriented grip portion 57 a bent in the form of reverse U-shape. Inoperation, when the grip portion 57 a is slightly lifted up and thenslightly pivoted to the right or left direction and then released frombeing lifted up, the positioning pin 58 b of the arm 58 is disengagedfrom the engaging hole 56 a (or 56 b) of the receiving plate 56 and thenrides onto the receiving plate 56. Under this condition where the lowerend of the positioning pin 58 b is in contact on the receiving plate 56,if the lock operating tool 57 is moved to slide the positioning pin 58 bon the receiving plate 56, the positioning pin 58 b will engage into theengaging hole 56 b (or 56 a) and at the same time, the lower end 57 b ofthe grip portion 57 a will engage into a lock position fixing portion59R (or the lock-releasing position fixing portion 59U) of thepositioning member 59, whereby the lock operating tool 57 will be fixedin position.

While the operating lever 26 is located at the neutral position, if thearm 58 is pivoted with an operation of the operating tool 57 toinsert/withdraw the lock pin 55 to/from the lock pin holes 51 a, 52 a ofthe brackets 51, 52 via the holding portion 55 a, the spool valves 23,24 will be locked or lock-released. On the right-hand side of thedriver's seat 4 and at an upper portion of the rear wheel fenders, thereis provided positioning means 59 including a lock position fixingportion 59R for fixing the grip portion 57 a at a lock position (r) anda lock-released position fixing portion 59U for fixing the position ofthe grip portion 59R at a lock-released position (u).

Under a non-work condition, with the operating lever 26 being set at theneutral position, as indicated by two-dot line in FIG. 4 and FIG. 6, thegrip portion 57 a of the lock operating tool 57 is operated to the outerside of the vehicle body to set the lower end 57 b of the grip portion57 a to the lock position fixing portion 59R, whereby the lock pin 55will be inserted into the pin holes 51 a, 52 a defined in the brackets51, 52 attached to the valve operating links 38, 39 of the spool valves23, 24 and inserted also into the boss portion 53 formed in the supportbracket 40, so that the operating lever 26 is mechanically fixed at theneutral position. Under a working condition, from the condition of theoperating lever 26 being mechanically fixed at the neutral position, asindicated by the solid line in FIG. 4 and FIG. 5, from the lockedcondition of the lock operating tool 57, the grip portion 57 a of thelock operating tool 57 will be set from the lock position fixing portion59R to the lock-released position fixing portion 59U, so that the lockpin 55 will be removed from the lock pin holes 51 a, 52 a of thebrackets 51, 52 of the operating links 38, 39, whereby the crisscrossoperations of the operating lever 26 are made possible.

As described above, with the hydraulic apparatus according to thisembodiment, the two spool valves 23, 24 for two hydraulic devices areoperably coupled to the single operating lever 26, which lever 26 isconfigured to be operable in the first direction (front/back direction)and the second direction (right/left direction) intersecting the firstdirection, so that with operations of the operating lever 26 in thefirst direction and the second direction, the spool valves 23, 24 areoperated separately and respectively. And, in the operative couplingmechanism between the two spool valves 23, 24 and the operating lever26, there are interposed the valve operating links 38, 39 respectivelycoupled to the valves 23, 24, and the pair of frame plates (supportbrackets 40, 41) disposed across the valve operating links 39, 38 hold,from the opposed ends, the boss portion 42 which supports the right/leftoriented support shaft 30 for operating the operating lever 26 in thefirst direction (front/back direction). The valve operating links 38, 39for respectively operating the two spool valves 23, 24 are pivotallysupported to the support shaft 45 provided in the pair of supportbrackets 40, 41 and the lock pin 55 is provided in the support bracket41 to be slidable relative thereto. The two valve operating links 38, 39form the pin holes 51 a, 52 a via the brackets 51, 52 formed integrallytherewith. When the two spool valves 23, 24 are at the neutralpositions, the lock pin 55 is inserted into the pin holes 51 a, 52 awith a locking operation by the lock operating tool 57, thus fixing thevalve operating links 38, 39, whereby the spool valves 23, 24 arelocked.

With the above, the boss portion 42 supporting the support shaft 30 ofthe operating lever 26 is held and clamped from the opposed sidesthereof by the pair of support brackets 40, 41 disposed across the valveoperating links 38, 39, so the support brackets 40, 41 per se are formedsturdy and the boss portion 42 too is firmly clamped and held by thesupport brackets 40, 41. Accordingly, even when the operating lever 26is operated in the two directions, there occurs no displacement orlooseness in the boss portion 42. Consequently, the support shaft 30 canbe maintained in a reliable manner and the operating lever 26 will notbe displaced from the first direction and the lever operations may becarried out smoothly and lightly.

When the two spool valves 23, 24 are located at the neutral positions,the two valve operating links 38, 39 are fixed simultaneously byinserting the single lock pin 55 into the plurality of pin holes 51 a,52 a formed in the two valve operating links 38, 39, thus locking thespool valves 23, 24. That is to say, the spool valves 23, 24 are lockedby inserting the single lock pin 55 into the holes 51 a, 52 a formed inthe two valve operating links 38, 39 provided respectively andseparately for operating the two spool valves 23, 24. Therefore, thevalve operating links 38, 39 for operating the spool valves 23, 24,whether the valve operated in the first direction (front/back direction)or the valve operated in the second direction (right/left direction),are locked in a reliable manner at the valve neutral positions, so thateven if there exists some play on the side of the operating lever 26,the spool valves 23, 24 can be locked reliably at the neutral positions.

Second Embodiment

FIGS. 10-16 show a work vehicle (tractor) according to a secondembodiment. In the following discussion, locking means different in thefollowing respects from the one in the foregoing first embodiment willbe described. The rest of the construction is identical to the mainembodiment.

As shown in FIG. 13 and FIG. 14, lock pin holes 50 are formedcontinuously in series through the two-forked arm portions 38 e, 39 e ofthe valve operating links 38, 39. A bracket 61 having a boss portion 54is attached to the support bracket 41 and into this boss portion 54,there is inserted a lock pin 55 having an engaging portion 55 b bent inthe shape of upwardly oriented L-shape. To the rear bracket 40, there isattached a bracket 63 forming a pin hole 62 which is located coaxiallywith the plurality of pin holes 50, when the operating lever 26 islocated at the neutral position. To the upper portion of the bracket 61,there is attached a horizontal receiving plate 56 forming an engaginghole 56 b, the receiving plate 56 being oriented more outward (frontside) than the support bracket 41.

As shown in FIG. 11, the working point on the side of the spool valve23, 24 (the position of the pin 47), the axis (a) (pivot) of thefront/back oriented support shaft 45, the axis of the lock pin 55, andthe coupling members 48 b, 49 b (power points) are aligned side by sidealong a straight line L in the rear view, and the lock pin 55 is locatedat the right/left intermediate portion between the front/back orientedsupport shaft 45 and the coupling members 48 b, 49 b. The arm 58provided at the lower end of the lock operating tool 57 includes a slot58 a for engagement with the reverse L-shaped holding portion 55 a and adownwardly oriented positioning pin 58 b.

When the lock operating tool 57 is located at the lock-released position(u), the downwardly oriented positioning pin 58 b formed on the arm 58is offset to the front side beyond the leading end (front end) of thereceiving plate 56, and the lower end of the positioning pin 58 b islocated lower than the upper face of the receiving plate 56. For lockingthe spool valve 23, 24 from this condition, the grip portion 57 a of thelock operating tool 57 will be slightly lifted up and slightly pivotedin the right direction and then lifting of the grip portion 57 a will bereleased, whereby the positioning pin 58 b of the arm 58 will ride overthe receiving plate 56. Under this condition of the lower end of thepositioning pin 58 b being in contact on the receiving plate 56, thelock operating tool 57 will be moved further to the right, thereby tocause the positioning pin 58 b to slide on the receiving plate 56, thepositioning pin 58 b will engage into the engaging hole 56 a and at thesame time the lower end 57 b of the grip portion 57 a will fit into thelock position fixing portion 59R, whereby the lock operating tool 57will be fixed in position. Under the locked condition, the valveoperating links 38, 39 are fixed with the lock pin 55 being insertedinto all of the pin holes 50 formed in the arm portions 38 e, 39 e andinto the pin hole 62 formed in the bracket 63, thus locking the spoolvalves 23, 24.

Incidentally, in the first and second embodiments, the spool valves 23,24 are employed as the switchover valve 25. Instead, rotary type valvesmay be employed.

Third Embodiment

FIGS. 17-22 show a work vehicle (tractor) according to a thirdembodiment. In this embodiment, FIG. 17 shows a partial side view of acabin type tractor mounting a front loader R. In this tractor, on afour-wheel driven type traveling vehicle body 103 including front wheels101 and rear wheels 102, there is mounted a cabin C including a driver'sseat 104, a front wheel steering wheel 105, a driver's access step 106,etc.

The traveling vehicle body 103 includes an engine (not shown) disposedinside a hood 111 provided at a front portion of the vehicle body, and afront frame 112 supporting the engine. Between the engine and atransmission case 109 disposed at a rear portion of the vehicle body, agear case 108 and an intermediate housing 110 formed of plate metal andhaving a hollow structure are disposed. Inside the cabin C, a pair of,right/left brake pedals 117 are provided on the right side and forwardlyof the driver's access step 106. At a rear portion of the transmissioncase 109, there are mounted a hydraulic driven type lift arm 113 and arear PTO shaft 114 for taking off power for a work implement (not shown)to be mounted to the rear portion.

To the front portion of the traveling vehicle body 103, the front loaderR is detachably connected. A hydraulic apparatus for driving this frontloader R is constructed as follows.

At a lateral portion of the transmission case 109 on the right side andat a lower position of the driver's seat 104, there are mounted a pairof switchover valves V, and inside the cabin C, an operating lever 126for switching over the switchover valves V extends upward from theposition of a lever operating mechanism A. The lever operating mechanismA is supported to the transmission case 109 and is attached to upper andlower frames 119, 120 disposed in the front/back direction along theinner side of the rear wheel fenders 118. The switchover valve Vincludes two, three-position switchover type, spool valves 123, 124mounted in juxtaposition in the front/back direction, to be operablycoupled with the operating lever 126 as will be described later. Withcrisscross operations of the operating lever 126, feeding/draining ofpressure oil to/from the two sets of hydraulic circuits (not shown) ispossible.

Referring to the front loader R, to a support frame 131 connected andfixed to front right/left portions of the traveling vehicle body 103, aboom 132 is connected to be vertically pivotable. And, a bucket 133 ispivotally connected to the leading end of the boom 132 to be capable ofpivotal dumping actions. And, a boom cylinder 134 and a bucket cylinder135 which comprise double-action type cylinders are connected andcommunicated to the valves 123, 124 via unillustrated oil passageways,respectively.

FIGS. 18-22 show a lever operating mechanism A for the operating lever126 and a locking mechanism B for the switchover valves V. As shown inFIG. 22, on the right side of the driver's seat 104, there is disposed afixed frame 140 having an outwardly opened angular U-shape in the planview, with its intermediate piece 140 c being located on the inner side,opposed pieces 140 a, 140 b being located on the front and back sides.The fixed frame 140 is a fixed portion fixed to the vehicle body. And,to this fixed frame 140 acting as the fixed portion, there are attachedthe lever operating mechanism A for operating the operating lever 126 inthe first direction (front/back direction) and the second direction(right/left direction) and the locking mechanism B for locking theoperating lever 126 at its neutral position.

The lever operating mechanism A is constructed as follows.

As shown in FIG. 21 and FIG. 22, the fixed frame 140 having an angularU-shape in the plan view includes a vehicle body rear side piece 140 a.To this piece 140 a, a fore/aft oriented boss 142 is fixed, with theboss 142 extending along the front/back oriented axis (x). To this boss142, a support shaft 130 is supported to be rotatable about thefront/back oriented axis (x), with a first operating tool 143 mountedthereon having an angular hook-like shape in plan view. To the firstoperating tool 143, a second operating tool 144 is pivoted to bepivotable about the right/left oriented axis (y). To the first operatingtool 143 too, a connecting portion 126 a of the operating lever 126 isfixed via a base end member 144 a attached erect on the upper face ofthe second operating tool 144 and via a connecting portion 144 b fixedto the upper end of the base member 144 a. The second operating tool 144is formed integral with the operating lever 126 to be movable togetherwith this operating lever 126 and constitutes the base portion of theoperating lever 126.

As shown in FIGS. 18-20, to the first operating tool 143, an operatingaim 143 a is connected, with the arm 143 being oriented to the rightouter side. To this operating arm 143 a, a valve 123 is operably coupledvia a push-pull wire 148 having a coupling member 148 a. Further, to thesecond operating tool 144, a valve 124 is operably coupled via apush-pull wire 149 having a coupling member 149 a.

Thus, when the operating lever 126 is operated to a neutral position(the intersection of the cross) in the front/back direction (firstdirection) and in the right/left direction (second direction), the twovalves 123, 124 will be located at the neutral positions. When the grip126 b of the operating lever 126 is moved from the neutral position tothe right or left side, the first operating tool 143 will be pivotedabout the front/back oriented axis (x), so that one valve 123 will beoperated. When the grip 126 b of the operating lever 126 is operatedfrom the neutral position to the front or the back side, the secondoperating tool 144 will be pivoted about the right/left oriented axis(y), so that the other valve 124 will be operated.

To the hydraulic circuit switched over by one valve 123, a boom cylinder134 is pipe-connected. To the hydraulic circuit switched over by theother valve 124, a bucket cylinder 135 is pipe-connected. Then, when thegrip portion 126 b of the operating lever 126 is operated from theneutral position to the front side, the boom cylinder 134 will becontracted to lower the boom 132. When the grip portion 126 b of theoperating lever 126 is operated from the neutral position to the backside, the boom cylinder 134 will be expanded to elevate the boom 132.When the grip portion 126 b of the operating lever 126 is operated fromthe neutral position to the right side, the bucket cylinder 135 will beexpanded to dump the bucket 133 downwards. When the grip portion 126 bof the operating lever 126 is operated from the neutral position to theleft side, the bucket cylinder 135 will be contracted to elevate thebucket 133 for scooping.

Next, the locking mechanism B will be explained in detail.

As shown in FIGS. 18-22, to the base end member 144 a formed erect onthe second operating tool 144, there is fixed a locking concave member151 forming a concave portion 151 a comprised of a cutout portion whichcuts out the end portion to render it open obliquely right, upperdirection, and there is provided a plate-like clamping member 152 havinga U-shaped cross section in the plan view and engaging this concavemember 151 by clamping it from its opposed sides, with the clampingmember 152 having a lock pin 55 engageable with the concave portion 151a.

The clamping member 152 is pivotally fixed to a support shaft 154 actingas a support portion supported to a front/back boss portions 153 formedrespectively in front and back side pieces 140 a, 140 b of the fixedframe 140 having a U-shaped cross section as seen in the plan view. Thesupport shaft 154 is operably coupled to a lock operating tool 156pivotally supported to the front side piece 140 b of to fixed frame 140and pivots the clamping member 152 for engagement with the concavemember 151 in response to an operation of the lock operating tool 156,thus locking the operating lever 126.

The support shaft 154 extends through the front/back boss portions 153on the fixed frame 140, and to the front end of the support shaft 154projecting forwardly of the front side piece 140 b, there is fixed anarm 157 having a pin 157 a at its free end. The lock operating tool 156forms an elongate slot 158 a for engagement with the pin 157 a, and at aposition downwardly of the elongate slot 158 a, there is fixed an arm158 having a positioning pin 158 b (corresponding to “holding means”)projecting toward the side of the side piece 140 b (to the back side).

Under the lock-released condition shown in FIG. 19 and FIG. 20 (a), forretaining the positioning pin 158 b to the side piece 140 b, the sidepiece 140 b forms a pin hole 159.

The lock operating tool 156 is inserted into a boss portion 160 providedin the side piece 140 b of the fixed frame 140 to be slidable in thefront/back direction. At the rear end of the lock operating tool 156, astopper 161 is provided, and between this stopper 161 and the rear endface of the boss portion 160, a spring 162 is interposed, so that thelock operating tool 156 is urged to the back side so as to retain thearm 158 in position, under the condition in contact with the front endof the boss portion 160.

As shown in FIGS. 20 (a), (b), when the locking mechanism B is under thelock-released condition (see FIG. 20 (a)), the positioning pin 158 bprovided in the arm 158 is in engagement with the pin hole 159 formed inthe side piece 140 b. With this, the locking mechanism B is maintainedunder the lock-released condition. For releasing this lock-releasedcondition, the lock operating tool 156 will be pulled to the front sideagainst the urging force of the spring 162 and the lock operating tool156 will be moved counter-clockwise from the condition in FIG. 20 (a).When the lock operating tool 156 is pulled out and pivotedcounter-clockwise slightly and then released, the positioning pin 158 bwhich has moved out of the pin hole 159 will ride over the front face ofthe side piece 140 b. Under this condition where the leading end of thepositioning pin 158 b is in contact with the front face of the sidepiece 140 b, the lock operating tool 156 will be moved to cause thepositioning pin 158 b to slide downward on the front face of the sidepiece 140 b, whereby the positioning pin 158 b will enter the spacedownwardly of the lower edge of the side piece 140 b, so that the lockoperating tool 156 will be fixed in position. With this, as illustratedfrom FIG. 20 (a) to FIG. 20 (b), the clamping member 152 is pivoteddownward and the clamping member 152 clamps the concave member 151 fromits opposed sides and the lock pin 155 is engaged with the concaveportion 151 a, thus realizing a locked condition. Under this lockedcondition, the positioning pin 158 b is placed in contact with the loweredge of the side piece 140 b, so that the locking mechanism B ismaintained under the locked condition.

For releasing the operating lever 126 from the locked condition, asillustrated from FIG. 20 (b) to FIG. 20 (a), from the locked conditionwhere the positioning pin 158 b projects into the space downwardly ofthe lower edge of the side piece 140 b, the lock operating tool 156 ispulled out against the urging force of the spring 162 and the lockoperating tool 156 is pivoted clockwise in the illustrated plane therebyto pivot the arm 158 upward with the leading end of the positioning pin158 b in sliding contact with the side piece 140 b, so that the lockingmechanism B is rendered into the lock-released condition shown in FIG.20 (a) and the locking mechanism B is maintained in position. With this,as shown in FIG. 20 (a), the clamping member 152 is pivoted upward tomove away from the concave member 151 and the lock pin 155 is moved awayfrom the concave portion 151 a.

As described above, according to the hydraulic apparatus of thisembodiment, the two valves 123, 124 for the two hydraulic units areoperably coupled to the single operating lever 126. And, this operatinglever 126 is operable in the first direction (front/back direction) andthe second direction (right/left direction) intersecting the firstdirection. And, the operating lever 126 is operated in the firstdirection and the second direction, so that the valves 123, 124 areoperated individually. And, there is provided the locking mechanism Bfor locking the operating lever 126 when the two valves 123, 124 arelocated at the neutral positions. This locking mechanism B is attachedto the second operating tool 144 of the operating lever 126, with theconcave member 151 forming the concave portion 151 a at the end thereof,with the clamping member 152 being attached to the support shaft 154 andengageable with the concave member 151 by clamping it from its opposedsides, and with the pin 155 being provided in the clamping member 152for the engagement with the concave portion 151 a. When the operatinglever 126 is located at the neutral position, the pivot shaft 154 isrotated to engage the concave member 151 between the pair of members 152a, 152 a of the clamping member 152, and the pin 155 provided in theclamping member 152 is engaged in the concave portion 151 a formed inthe concave member 151, so that the operating lever 126 is locked to beimmovable both in the first direction and the second direction.

With the above arrangement, with the clamping of the concave member 151by the clamping member 152 (first engagement), the operating lever 126is locked against its movement in the first direction (front/backdirection). And, with the engagement between the concave portion 151 aof the concave member 151 and the pin 155 of the clamping member 132(second engagement), the operating lever 126 is locked against itsmovement in the second direction (right/left direction). Hence, thelocking of the operating lever 126 in the first direction and the seconddirection can be effected in a reliable manner, and the lever operationscan be effected smoothly and lightly.

Incidentally, in the third embodiment, the concave member 151 having theconcave portion 151 a is provided at the base portion 144 of theoperating lever 126, whereas the clamping member 152 having the pin 155is provided in the support portion (support shaft 154). Instead, theconcave member 151 and the clamping member 152 may be arranged viceversa, so that the clamping member 152 is provided in the base portion144 of the operating lever 126, and the concave member 151 is providedin the support portion (support shaft 154).

Further, in the third embodiment, the clamping member 152 having the pin155 is fixed to the support shaft 154, and with pivoting of the clampingmember 152 about the support shaft 154, its engagement with the concavemember 151 having the concave portion 151 a is realized. Instead, theclamping member 152 may be guided by an unillustrated guiding member tomove linearly to engage/disengage with/from the concave member 151. Or,the clamping member 152 may be moved as being driven by a driving unitsuch as an unillustrated cylinder, motor or the like, toengage/disengage with/from the concave member 151.

Further, in the third embodiment, the clamping member 152 is formed bybending a plate into the U-shape. Instead, this clamping member 152 maybe formed by connecting together two plates spaced apart from eachother.

The present invention is applicable not only to a tractor having thefront loader R, but also to a tractor having a snow removing apparatusor a grass mowing apparatus.

What is claimed is:
 1. A work vehicle having a hydraulic apparatus,comprising: a single operating lever; a first valve operable by anoperation of the operating lever in a first direction; a second valveoperable by an operation of the operating lever in a second directionintersecting the first direction; a locking mechanism for locking theoperating lever at a neutral position thereof, the locking mechanismincluding: a concave member attached to one of a movable support portionand a base portion of the operating lever, the concave member defining aconcave portion at an end thereof; a clamping member attached to theother of the movable support portion and the base portion of theoperating lever for clamping the concave member, the clamping memberincluding a pin engageable with the concave portion; wherein, when theoperating lever is at the neutral position, the operating lever islocked to be immovable in the first or second direction by moving thesupport portion to cause the clamping member to clamp the concave memberand also to cause the pin to engage the concave portion.
 2. The workvehicle according to claim 1, wherein: the support portion comprises apivotable and fixable support shaft, and when the operating lever islocated at the neutral position, the operating lever is locked to beimmovable in the first or second direction by pivoting the supportshaft.
 3. The work vehicle according to claim 1, further comprisingholding means for holding a locked condition provided by the engagementbetween the concave member and the clamping member and also holding alock-released condition provided by detachment between the concavemember and the clamping member.